The present invention relates to a power supply for an electronic device such as a large scale electronic computer, etc. and in particular to a power supply capable of effecting easily a working margin test for LSIs in the electronic device by feeding it with power from a plurality of AC power supplies.
Since an electronic device such as a large scale electronic computer, etc. consumes high electric power, current intensity of a power supply thereto is as high as several thousands of amperes. In order to feed it stably with such electric power, an AC stabilizing device such as an MG (Motor Generator) set, etc. is used, which stabilizes commercial AC, and this stabilized AC is rectified by a DC power supply, which converts it into a DC having a required voltage. As disclosed by JP - A - Hei 1 - 120098, the DC thus obtained is supplied to logic units constituting the electronic device by means of a bus bar made of copper having a large current capacity.
Since a significant power supply ripple (pulsating component) is superposed usually on this DC obtained by rectification in the DC power supply, it is tried to reduce the power supply ripple by using an inductance of the bus bar and a smoothing condenser mounted between a bus bar for each of different voltages and a reference potential bus bar in the neighborhood of the logic units.
The reference potential bus bar is used in common for all the DC voltages in order to make the reference potential uniform within the logic units and to simplify the construction thereof.
Heretofore one AC power supply was disposed for each of the logic units to feed it with electric power.
In an electronic device using such a power supply, in the case where a working margin test is effected for LSIs in the logic units, there are no problems e.g. for a test effected by increasing or decreasing simultaneously all the voltages applied to the different logic units by a predetermined ratio, but for a test effected by increasing only specified voltages among the plurality of voltages by a predetermined ratio and decreasing the other voltages by another predetermined ratio or vice versa, one AC power supply cannot deal therewith. Therefore one or a plurality of other AC power supplies were provided and the test was effected by connecting them newly with a plurality of DC power supplies within the power supply.
As described above, by such a prior art power supply, it was necessary to reconnect the AC power supplies, every time a working margin test was effected for LSIs in the different logic units, which was troublesome and worsened operation efficiency.